V. Results
5.2 Corrosion behavior
5.2.3 Metal loss
The definition of metal loss is as below:
∆t (initial base metal − base metal after exposure )
2 [μm]
The thickness of initial base metal was measured before exposure to gallium. After testing, specimens was mounted, and sectioned to examination the cross-section of specimens, then the thickness of base metal remaining was measured at six region, and averaged.
Bare metal specimens showed much higher metal loss than other pre-oxidized specimens in gallium environment shown in Figs. 4.20~21. Metal loss decreased in gallium alloy environments as shown in Figs. 4.22~25.
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(a) (e)
(b) (f)
(c) (g)
(d) (h)
Fig. 4.1 Optical images of specimens after exposure to static gallium for 17(a), 140(b), 307(c), and 700(d) hr in air condition and 17(e), 140(f), 307(g), and 700(h) hr in vacuum condition, respectively.
40
(a) (e)
(b) (f)
(c) (g)
(d) (h)
Fig. 4.2 Optical images of specimens pre-oxidized at 500°C air for 24hr, after exposure to static gallium for 17(a), 140(b), 307(c), and 700(d) hr in air condition and 17(e), 140(f), 307(g), and 700(h) hr in vacuum condition, respectively.
41
(a) (e)
(b) (f)
(c) (g)
(d) (h)
Fig. 4.3 Optical images of specimens pre-oxidized at 500°C controlled O2 for 24 hr, after exposure to static gallium for 17(a), 140(b), 307(c), and 700(d) hr in air condition and 17(e), 140(f), 307(g), and 700(h) hr in vacuum condition, respectively.
42
(a) (e)
(b) (f)
(c) (g)
(d) (h)
Fig. 4.4 Optical images of specimens pre-oxidized at 500°C air for 100hr, after exposure to static gallium for 17(a), 140(b), 307(c), and 700(d) hr in air condition and 17(e), 140(f), 307(g), and 700(h) hr in vacuum condition, respectively.
43
(a) (e)
(b) (f)
(c) (g)
(d) (h)
Fig. 4.5 Optical images of specimens after exposure to gallium alloy (Ga-14Sn-6Zn) for 17(a), 140(b), 307(c), and 700(d) hr in air condition and 17(e), 140(f), 307(g), and 700(h) hr in vacuum condition, respectively.
44
Base metal, tested at 500?
Pre-oxidized at 500? air for 24hr, tested at 500?
Pre-oxidized at 500? controlled O2 for 24hr, tested at 500?
Pre-oxidized at 500? air for 100hr, tested at 500?
Fig. 4.6 Weight change of vary specimens exposed to static gallium at 500°C, tested in air condition
0 100 200 300 400 500 600 700 800
Base metal, tested at 500?
Pre-oxidized at 500? air for 24hr, tested at 500?
Pre-oxidized at 500? controlled O2 for 24hr, tested at 500?
Pre-oxidized at 500? air for 100hr, tested at 500?
Fig. 4.7 Weight change of vary specimens exposed to static gallium at 500°C, tested in vacuum condition
45 Base metal, tested at 500?
Pre-oxidized at 500? air for 24hr, tested at 500?
Pre-oxidized at 500? air for 100hr, tested at 500?
Fig. 4.8 Weight change of vary specimens exposed to gallium alloy (Ga-14Sn-6Zn) at 500°C, tested in air condition Base metal, tested at 500?
Pre-oxidized at 500? air for 24hr, tested at 500?
Pre-oxidized at 500? air for 100hr, tested at 500?
Fig. 4.9 Weight change of vary specimens exposed to gallium alloy (Ga-14Sn-6Zn) at 500°C, tested in vacuum condition
46 Base metal, tested at 500?
Pre-oxidized at 500? air for 24hr, tested at 500?
Pre-oxidized at 500? air for 100hr, tested at 500?
Fig. 4.10 Weight change of vary specimens exposed to gallium alloy (Ga-8Sn-6Zn) at 500°C, tested in air condition Base metal, tested at 500?
Pre-oxidized at 500? air for 24hr, tested at 500?
Pre-oxidized at 500? air for 100hr, tested at 500?
Fig. 4.11 Weight change of vary specimens exposed to gallium alloy (Ga-8Sn-6Zn) at 500°C, tested in vacuum condition
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0 50 100 150 200 250 300 350
-300 -200 -100 0 100 200 300
Weight change (mg/cm2)
Exposure time (h) Base metal, tested at 500? (Gallium environment)
Pre-oxidized at 500? air for 24hr, tested at 500? (Gallium environment) Base metal, tested at 500? (Gallium alloy environment) : Ga-14Sn-6Zn
Fig. 4.12 Weight change of vary specimens exposed to gallium and gallium alloy (Ga-14Sn-6Zn) at 500°C, tested in controlled O2 condition
48
Base metal, tested at 500?
Pre-oxidized at 500? air for 24 hr, tested at 500Pre-oxidized at 500? air for 24 hr, tested at 500?
Pre-oxidized at 500? controlled O2 for 24 hr, tested at 500?
Pre-oxidized at 500? air for 100 hr, tested at 500?
Fig. 4.13 Thickness of reaction layer formed on the surface of specimens in gallium environment tested in air condition
0 100 200 300 400 500 600 700 800
Base metal, tested at 500?
Pre-oxidized at 500? air for 24 hr, tested at 500Pre-oxidized at 500? air for 24 hr, tested at 500?
Pre-oxidized at 500? controlled O2 for 24 hr, tested at 500?
Pre-oxidized at 500? air for 100 hr, tested at 500?
Fig. 4.14 Thickness of reaction layer formed on the surface of specimens in gallium environment tested in vacuum condition
49 Base metal, tested at 500?
Pre-oxidized at 500? air for 24hr, tested at 500?
Pre-oxidized at 500? air for 100hr, tested at 500?
Fig. 4.15 Thickness of reaction layer formed on the surface of specimens in gallium alloy environment (Ga-14Sn-6Zn) tested in air condition
0 100 200 300 400 500 600 700 800 Base metal, tested at 500?
Pre-oxidized at 500? air for 24hr, tested at 500?
Pre-oxidized at 500? air for 100hr, tested at 500?
Fig. 4.16 Thickness of reaction layer formed on the surface of specimens in gallium alloy environment (Ga-14Sn-6Zn) tested in vacuum condition
50 Base metal, tested at 500?
Pre-oxidized at 500? air for 24hr, tested at 500?
Pre-oxidized at 500? air for 100hr, tested at 500?
Fig. 4.17 Thickness of reaction layer formed on the surface of specimens in gallium alloy environment (Ga-8Sn-6Zn) tested in air condition
0 100 200 300 400 500 600 700 800 Base metal, tested at 500?
Pre-oxidized at 500? air for 24hr, tested at 500?
Pre-oxidized at 500? air for 100hr, tested at 500?
Fig. 4.18 Thickness of reaction layer formed on the surface of specimens in gallium alloy environment (Ga-8Sn-6Zn) tested in vacuum condition
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0 50 100 150 200 250 300 350
200 250 300 350 400 450 500 550
Reaction layer (um)
Exposure time (h) Base metal, tested at 500? (Gallium environment)
Pre-oxidized at 500? air for 24hr, tested at 500? (Gallium environment) Base metal, tested at 500? (Gallium alloy environment) : Ga-14Sn-6Zn
Fig. 4.19 Thickness of reaction layer formed on the surface of specimens in gallium and gallium alloy environment (Ga-14Sn-6Zn) at 500°C, tested in controlled O2 condition
52
Base metal, tested at 500?
Pre-oxidized at 500? air for 24hr, tested at 500?
Pre-oxidized at 500? controlled O2 for 24hr, tested at 500?
Pre-oxidized at 500? air for 100hr, tested at 500?
Fig. 4.20 Metal loss of specimens in gallium environment tested in air condition
0 100 200 300 400 500 600 700 800
Base metal, tested at 500?
Pre-oxidized at 500? air for 24hr, tested at 500?
Pre-oxidized at 500? controlled O2 for 24hr, tested at 500?
Pre-oxidized at 500? air for 100hr, tested at 500?
Fig. 4.21 Metal loss of specimens in gallium environment tested in vacuum condition
53 Base metal, tested at 500?
Pre-oxidized at 500? air for 24hr, tested at 500?
Pre-oxidized at 500? air for 100hr, tested at 500?
Fig. 4.22 Metal loss of specimens in gallium alloy environment (Ga-14Sn-6Zn) tested in air condition
0 100 200 300 400 500 600 700 800 Base metal, tested at 500?
Pre-oxidized at 500? air for 24hr, tested at 500?
Pre-oxidized at 500? air for 100hr, tested at 500?
Fig. 4.23 Metal loss of specimens in gallium alloy environment (Ga-14Sn-6Zn) tested in vacuum condition
54 Base metal, tested at 500?
Pre-oxidized at 500? air for 24hr, tested at 500?
Pre-oxidized at 500? air for 100hr, tested at 500?
Fig. 4.24 Metal loss of specimens in gallium alloy environment (Ga-8Sn-6Zn) tested in air condition
0 50 100 150 200 250 300 350 Base metal, tested at 500?
Pre-oxidized at 500? air for 24hr, tested at 500?
Pre-oxidized at 500? air for 100hr, tested at 500?
Fig. 4.25 Metal loss of specimens in gallium alloy environment (Ga-8Sn-6Zn) tested in vacuum condition
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Fig. 4.26 SEM Images of SS 316L after exposure to static gallium at 500°C in air for 17, 140, 307, and 700 hrs, along red (steel region) and blue (gallium compound region) spots indicating analysis positions for EPMA (left) and quantitative analysis of Fe, Cr, O, Ga, and Ni obtained by EPMA (right).
-20 -10 0 10 20
56
Fig. 4.27 SEM Images of SS 316L after exposure to static gallium at 500°C in vacuum for 17, 140, 307, and 700 hrs, along red (steel region) and blue (gallium compound region) spots indicating
57
Fig. 4.28 SEM Images of pre-oxidized SS 316L at 500°C air for 24hr, after exposure to static gallium at 500°C in air for 17, 140, 307, and 700 hrs, along red (steel region) and blue (gallium compound region) spots indicating analysis positions for EPMA (left) and quantitative analysis of Fe, Cr, O, Ga, and Ni obtained by EPMA (right).
-20 -10 0 10 20
58
Fig. 4.29 SEM Images of pre-oxidized SS 316L at 500°C air for 24hr, after exposure to static gallium at 500°C in vacuum for 17, 140, 307, and 700 hrs, along red (steel region) and blue (gallium compound region) spots indicating analysis positions for EPMA (left) and quantitative analysis of Fe, Cr, O, Ga, and Ni obtained by EPMA (right).
59
Fig. 4.30 SEM Images of pre-oxidized SS 316L at 500°C controlled O2 for 24hr, after exposure to static gallium at 500°C in air for 17, 140, 307, and 700 hrs, along red (steel region) and blue (gallium compound region) spots indicating analysis positions for EPMA (left) and quantitative analysis of Fe, Cr, O, Ga, and Ni obtained by EPMA (right).
-20 -10 0 10 20
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Fig. 4.31 SEM Images of pre-oxidized SS 316L at 500°C controlled O2 for 24hr, after exposure to static gallium at 500°C in vacuum for 17, 140, 307, and 700 hrs, along red (steel region) and blue (gallium compound region) spots indicating analysis positions for EPMA (left) and quantitative analysis of Fe, Cr, O, Ga, and Ni obtained by EPMA (right).
-20 -10 0 10 20
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Fig. 4.32 SEM Images of pre-oxidized SS 316L at 500°C air for 100hr, after exposure to static gallium at 500°C in air for 17, 140, 307, and 700 hrs, along red (steel region) and blue (gallium compound region) spots indicating analysis positions for EPMA (left) and quantitative analysis of Fe, Cr, O, Ga, and Ni obtained by EPMA (right).
-20 -10 0 10 20
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Fig. 4.33 SEM Images of pre-oxidized SS 316L at 500°C air for 100hr, after exposure to static gallium at 500°C in vacuum for 17, 140, 307, and 700 hrs, along red (steel region) and blue (gallium compound region) spots indicating analysis positions for EPMA (left) and quantitative analysis of Fe, Cr, O, Ga, and Ni obtained by EPMA (right).
-20 -10 0 10 20
63
Fig. 4.34 SEM Images of SS 316L after exposure to static gallium alloy (Ga-14Sn-6Zn) at 500°C in air for 17, 140, 307, and 700 hrs, along red (steel region) and blue (gallium compound region) spots indicating analysis positions for EPMA (left) and quantitative analysis of Fe, Cr, O, Ga, Ni, Sn and Zn obtained by EPMA (right).
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Fig. 4.35 SEM Images of SS 316L after exposure to static gallium alloy (Ga-14Sn-6Zn) at 500°C in vacuum for 17, 140, 307, and 700 hrs, along red (steel region) and blue (gallium compound region) spots indicating analysis positions for EPMA (left) and quantitative analysis of Fe, Cr, O, Ga, Ni, Sn and Zn obtained by EPMA (right).
-20 -10 0 10 20
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REFERENCES
1. Luebbers, PR 1993, ‘Compatibility of ITER candidate structural materials with static gallium’, Argonne National Laboratory, U.S DOE
2. Yatsenko, SP 1970, ‘Solubility of metals of fifth period in liquid gallium’, Sov. Mater. Sci., Vol. 6 3. Prokhorenko V 2000, ‘Liquid gallium: potential uses as a heat-transfer agent’, High temperature, Vol. 38,
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